﻿<TreeView TItem="TreeFoo" Items="@ExpandItems" ShowCheckbox="true" />

@code {
    private List<TreeViewItem<TreeFoo>> ExpandItems { get; set; } = GetExpandItems();

    private static List<TreeViewItem<TreeFoo>> GetExpandItems()
    {
        var ret = TreeFoo.GetTreeItems();
        ret[1].IsExpand = true;
        return ret;
    }
}
